      subroutine Flux(U_1,F_1,n)
	  use global
      Implicit none
	  integer :: n,i,ie,nelt
	  
	  !!! Define the dimension and type of the vectors
	  Dimension U_1(n,3), F_1(n,3),Pres_1(n)
	  Real(8) :: U_1,F_1,Pres_1
	  
	  !!! Get the flux vectors in the form of solution vectors
	  do i=1,n
		Pres_1(i)=(gam-1.d0)*(U_1(i,3)-0.5D0*U_1(i,2)*U_1(i,2)/U_1(i,1))
		F_1(i,1)=U_1(i,2)
		F_1(i,2)=U_1(i,2)*U_1(i,2)/U_1(i,1)+Pres_1(i)
		F_1(i,3)=(U_1(i,3)+Pres_1(i))*U_1(i,2)/U_1(i,1)
	  enddo

      end subroutine